<!DOCTYPE html>
<div style="position:absolute; will-change:transform; contain:strict; height:500px;">
  <div style="position:relative; width:420px; border:2px solid black; height:200px;">
    <div style="opacity:0.5;">
      <div style="height:200px; background:green; position:absolute; width:200px; left:0; top:0;"></div>
      <div style="height:200px; background:green; position:absolute; width:200px; right:0; top:0;"></div>
      <div style="position:fixed; height:98px; width:98px; left:170px; top:220px; background:green; border:1px solid lime;"></div>
    </div>
  </div>
</div>
